Solenoid-operated starting motor

ABSTRACT

In a solenoid circuit for a staring motor, a solenoid has both a pull-in coil and a hold-in coil for positioning an armature to effect engagement and disengagement of the starting motor with an engine. Shifting of the armature also closes a parallel circuit between an electrical source and the starting motor. A diode is arranged in series with one end of the pull-in coil to prevent reverse current flow through the pull-in coil and the development of a magnetomotive force therein counter to force developed by the hold-in coil.

United States Patent James P. Welsh Morton, lll.

Sept. 18, 1970 Sept. 28, 1971 Caterpillar Tractor Co. Peoria, lll.

inventor Appl. No. Filed Patented Assignee SOLENOID-OPERATED STARTING MOTOR 3 Claims, 2 Drawing Figs.

noz 1/10 290/38, 48, mo. 1, mo. 4

References Cited UNITED STATES PATENTS 7 /1952 Bolles l 290/38 3,433,968 3/1969 Broyden Primary Examiner-Gris L. Rader Assistant Examiner-W. E. Duncanson, Jr. Attorney-Fryer, Tjensvold, Feix, Phillips & Lempio ABSTRACT: In a solenoid circuit fora staring motor, a solenoid has both a pull-in coil and a hold-in coil for positioning an armature to effect engagement and disengagement of the starting motor with an engine. Shifting of the armature also, closes a parallel circuit between an electrical source and the starting motor. A diode is arranged in series with one end of the pull-in coil to prevent reverse current flow through the pull-in coil and the development of a magnetomotive force therein counter to force developed by the hold-in coil.

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I: E -E- INVENTORS JAMES F. WELSH 1; 2:64 7) IATZORNEYS.

SOLENOID-OPERATED STARTING MOTOR US. Pat. No. 3,433,968, issued Mar. 18, 1969, describes a generally similar starting system including an additional resistive circuit arranged in parallel with the solenoid and in series with the starting motor to slowly rotate the starting motor as it enters into meshing engagement with an engine to assure proper indexing for the gear train of the starting motor.

The present invention relates to solenoid-operated starting motors and more particularly to a solenoid circuit including means for maintaining the starting motor either in positive engagement or disengagement with an engine. More particularly, the solenoid of such a system includes an armature which is operated by botha pullin coil and a hold-in coil for effectingengagement between the starting motor and an engine to be cranked by the starting motor. Shifting of the armature also preferably causes engagement between a movable contact plate and two contact points to close an additional electrical path for operating the motor. In such an arrangement, it has been found that reverse current flow through the pull-in coil causing a chattering effect with the armature rapidly shifting back and forth between its engaged and disengaged positions. This effect may lead to failure of the contact points or may cause the points to become welded to the contact point, either of which would make the starting motor inoperable. To overcome this problem, the present invention also contemplates the arrangement of diode means in series with the pull-in coil to prevent such current reversal.

Accordingly, it is an object of the present invention to provide a solenoid-operated starting motor including means for achieving positive engagement or disengagement of the starting with an engine to be cranked.

It is a further object of the invention to provide diode means in series with the pull-in coil for such a solenoid to prevent the development of counter magnetomotive forces within the pull-in coil and hold-in coil of the solenoid.

Other objects and advantages of the invention are made apparent in the following description having reference to the accompanying drawing.

In the drawing:

FIG. I is a generally schematic representation of a solenoidoperated starting motor, and

FIG. 2 represents an equivalent circuit for the arrangement of FIG. 11. The starting system illustrated in FIG. 1 represents a preferred embodiment constructed in accordance with the present invention. The system includes a starting motor 11 which is used to drive an engine gear component 12 for cranking an engine (not otherwise shown). The motor 11 is selectively coupled with the gear 12 by means of a movable pinion assembly 13.

A solenoid 14 includes a pull-in coil 16 and a hold-in coil 17 arranged about a movable armature 18. The armature 18 has an extension 19 pivoted to a member 21 which may be rotated about a pivot point 22 for engaging or disengaging the pinion assembly 13 with respect to the gear 12.

An electrical source, such as the battery indicated at 23, is effective to energize both the solenoid 14 and the starting motor 11 under the regulation of a control or starting switch 24. Energization of the two coils l6 and 17 shifts the armature 18 to the left (as viewed in FIG. 1), thus causing the pinion assembly 13 to enter into engagement with the gear 12.

Initial current for energizing the motor 11 passes through the pull-in coil 16. However, an additional circuit is provided to supply current for energizing the motor 11 once the armature I8 is shifted to engage the pinion assembly with the gear 12. For this purpose, a spring-loaded electrical contact plate 26 is arranged in spaced-apart relation from the left end of the armature 18. A pair of electrical contact points 27 and 28 is then arranged behind the contact plate 26. The battery 23 is connected in series across the switch 24 by means of an electrlcal conduit 29 with one end 16a of the pull-in coil 16 and one end 17a of the hold-in coil 17. A parallel line 31 connects the source 23 with the electrical contact point 27. The other end 16!) of the pull-in coil is connected in series with the electrical contact point 28 and the motor 11 to the other side of the battery 23 by means of electrical conduits 32 and 33. The other end 17b of the hold-in coil is connected with an electrical conduit 34 arranged in parallel with the electricalcontact point 28 and the motor 11 to provide a return line between the hold-in coil and the source 23.

In operation, closing of the switch 24 energizes both of the coils l6 and 17 with current for initially operating the motor 11 passing through the pull-in coil 16 and the conduits 32 and 33. The pull-in coil 16 is effective to shift the armature 18 leftwardly for engaging the pinion assembly 13 with the gear 12. Leftward movement of the armature also causes the contact plate 26 to engage both of the electrical points 27 and 28 providing an alternate circuit between the source 23 and motor 11 by means of conduits 31, 32 and 33. After the armature is shifted completely to the left and the pinion assembly is engaged with the gear 12, this alternate circuit carries the current for energizing the motor 11 to cause rotation of the gear 12.

Within such an arrangement, it has been found that once contact is made between the contact plate 26 and the electrical point 28, reverse current flow often occurs within the pullin coil 16 developing a magnetomotive force counter to the magnetomotive force developed by the hold-in coil 17 for maintaining the armature in its leftward position. This counter force may tend to shift the armature momentarily toward the right as viewed in FIG. 1. Upon the resulting circuit break between the electrical points 27 and 28, a positive force would again be developed by the pull-in coil rapidly shifting the armature again to the left. This sequence tends to occur very rapidly resulting in a chattering effect with the armature l8 rapidly shifting into and out of engagement with the contact plate 26 leading to possible failure of the starting motor in the manner described above. To prevent this effect, a diode 41 is arranged in series between the other end I6b of the pull'in coil and the contact point 28 to prevent the occurrence of such reverse current flow.

The problem referred to above may be more clearly seen having reference to the equivalent circuit shown in FIG. 2. R, equals the circuit resistance of the switch 24 and R, equals circuit resistance between the battery 23 and the contact points 27 and 28. The other components of the equivalent circuit in FIG. 2 are represented by the same numerals employed to designate those same components in FIG. 1.

During operation of the circuit, voltage achieved at the electrical point contact 28 is indicated as E, and voltage occurring at the junction of coils 16 and 17 (where their one ends 16a and 17a join with the conduit 29) is indicated by E,. It may be noted that both of these voltages are developed after closing of the switch 24. When R, is equal to R,, and plate 26 abuts both the electrical points 27, 28, the voltage at E is equal to the voltage at E Accordingly, the pull-in coil 16 is shorted out and the hold-in coil 17 remains effective to restrain the armature 18 in its leftwardly shifted position. However, if circuit resistance should develop so that R is greater than R, under the above conditions, E, would also be greater than E, because of the voltage drop across R Such an occurrence would cause reverse current flow through the pullin coil 16 developing a magnetomotive force in opposition to the magnetomotive force of the hold-in coil 17. Because of the heavier construction of the pull-in coil 16, the armature 18 would tend to momentarily shift to the right permitting the contact plate 26 to break engagement with the points 27 and 28.

E, would then become greater than E, and the pull-in coil would again shift the armature l8 leftwardly with a rapid sequence of these events resulting to cause chattering of the armature 18.

The arrangement of the diode 41 prevents the development of reverse current flow through the pull-in coil 16 under such circumstances. Accordingly, the chattering" action of the armature is prevented and reliability of the solenoid circuit is substantially enhanced.

What is claimed is:

1. A solenoid circuit for a starting motor, the solenoid having a pull-in coil and a hold-in coil, both coils being operatively coupled with a solenoid armature which is effective to shift a pinion mechanism for accomplishing positive engagement and disengagement of the starting motor with a gear component of an engine in response to energization of the coils by electrical source means and switch means, the armature also being arranged for providing electrical continuity between two contact points electrically arranged in parallel with the switch means and solenoid coils for energizing the motor by the electrical source means, the circuit comprising a series connection between the source and one end of each coil through the switch, parallel connecting means between the opposite ends of the coils and the source, a diode being in series communication with the other end of the pull-in coil to prevent reverse current flow through the pull-in coil and the development of a magnetomotive force in the pull-in coil counter to the magnetomotive force of the hold-in coil which maintains the shifted position of the armature for operation of the starting motor.

2. A solenoid circuit for a starting motor, the solenoid having a pull-in coil and a hold-in coil, both coils being operatively coupled with a solenoid armature which is effective to shift a pinion mechanism for accomplishing positive engagement and disengagement of the starting motor with a gear component of an engine in response to energization of the coils by electrical source means and switch means, the armature also being arranged for positioning a movable contact plate to provide electrical continuity between two contact points for operatively coupling the source with the starting motor, the circuit comprising a series connection between the source and one end of each coil through the switch, a connection between the source and one of the contacts, a series connection between the other end of the pull-in coil and the source through the other contact and the starting motor, a connection between the other end of the hold-in coil and the source in parallel with the series connection for the other end of the pull-in coil, the other contact and the motor and a diode ar ranged in the series connection for the other end of the pull-in coil to prevent reverse current flow through the pull-in coil and the development of a magnetomotive force in the pull-in coil in opposition to a magnetomotive force in the hold-in coil which maintains the shifted position of the armature for operation of the starting motor.

3. The circuit of claim 2 wherein the diode is arranged in the series connection between the other end of the pull-in coil and the other contact. 

1. A solenoid circuit for a starting motor, the solenoid having a pull-in coil and a hold-in coil, both coils being operatively coupled with a solenoid armature which is effective to shift a pinion mechanism for accomplishing positive engagement and disengagement of the starting motor with a gear component of an engine in response to energization of the coils by electrical source means and switch means, the armature also being arranged for providing electrical continuity between two contact points electrically arranged in parallel with the switch means and solenoid coils for energizing the motor by the electrical source means, the circuit comprising a series connection between the source and one end of each coil through the switch, parallel connecting means between the opposite ends of the coils and the source, a diode being in series communication with the other end of the pull-in coil to prevent reverse current flow through the pull-in coil and the development of a magnetomotive force in the pull-in coil counter to the magnetomotive force of the hold-in coil which maintains the shifted position of the armature for operation of the starting motor.
 2. A solenoid circuit for a starting motor, the solenoid having a pull-in coil and a hold-in coil, both coils being operatively coupled with a solenoid armature which is effective to shift a pinion mechanism for accomplishing positive engagement and disengagement of the starting motor with a gear component of an engine in response to energization of the coils by electrical source means and switch means, the armature also being arranged for positioning a movable contact plate to provide electrical continuity between two contact points for operatively coupling the source with the starting motor, the circuit comprising a series connection between the source and one end of each coil through the switch, a connection between the source and one of the contacts, a series connection between the other end of the pull-in coil and the source through the other contact and the starting motor, a connection between the other end of the hold-in coil and the source in parallel with the series connection for the other end of the pull-in coil, the other contact and the motor and a diode arranged in the series connection for the other end of the pull-in coil to prevent reverse current flow through the pull-in coil and the development of a magnetomotive forCe in the pull-in coil in opposition to a magnetomotive force in the hold-in coil which maintains the shifted position of the armature for operation of the starting motor.
 3. The circuit of claim 2 wherein the diode is arranged in the series connection between the other end of the pull-in coil and the other contact. 